Pseudohalogen Resurfaced CsPbBr₃ Nanocrystals for Bright, Efficient, and Stable Green-Light-Emitting Diodes

Abstract

Lead halide perovskite nanocrystals (LHP NCs) are regarded as promising emitters for next-generation ultrahigh-definition displays due to their high color purity and wide color gamut. Recently, the external quantum efficiency (EQE) of LHP NC based light-emitting diodes (PNC LEDs) has been rapidly improved to a level required by practical applications. However, the poor operational stability of the device, caused by halide ion migration at the grain boundary of LHP NC thin films, remains a great challenge. Herein, we report a resurfacing strategy via pseudohalogen ions to mitigate detrimental halide ion migration, aiming to stabilize PNC LEDs. We employ a thiocyanate solution processed post-treatment method to efficiently resurface CsPbBr3 NCs and demonstrate that the thiocyanate ions can effectively inhibit bromide ion migration in LHP NC thin films. Owing to thiocyanate resurfacing, we fabricated LEDs with a high EQE of 17.3%, a maximum brightness of 48000 cd m–2, and an excellent operation half-life time.

Achieving High Moisture Tolerance in Pseudohalide Perovskite Nanocrystals for Light-Emitting Diode Application

“…After storing the films for 5 days under ambient conditions, the PL properties were only slightly altered (e.g., red shift in the emission peak and 10% drop in the PLQY), showing enhanced stability compared to pristine NCs, which exhibited a red shift of 20 nm in the emission and a PLQY reduction of more than 50%. Notably, previous studies on hybrid perovskites have demonstrated improvement in PLQY up to 60% upon the incorporation of SCN – , , whereas inorganic perovskite have shown up to 45%, suggesting that hybrid pervovskite have more potential for further optimization. Upon post-treatment, the absorption spectra exhibited a sharp excitonic peak at 420 nm with an absorption edge at 512 nm, corresponding to the emission peaks at 435 (low intensity) and 520 nm, respectively (Figure c).…”

Mitigating halide ion migration by resurfacing lead halide perovskite nanocrystals for stable light-emitting diodes

“…11c). 97 The induced thiocyanate ions can not only fill the surface halide vacancies, but also increase the migration barrier of halide vacancies to block the movement of bromide ions. Thanks to the thiocyanate modified LHP NC films’ resistance to ion migration driven by an electric field, the fabricated PNC LED showed a good operation T 50 lifetime of 123 minutes @ 1000 cd m −2 .…”

Surface polarization-induced emission and stability enhancement of CsPbX3nanocrystals

“…14–20 Therefore, much effort has been dedicated to passivate the surface of CsPbX 3 NCs by introducing various kinds of ligands with enhanced bonding energy, such as trioctylphosphine (TOP), 21 2,2′-iminodibenzoic acid (IDA), 22 glutathione, 23 4-bromo-butyric acid, 24 etc. 25–32…”